Using a high-resolution mesoscale coupled model to simulate the 1996 Buffalo Creek flash-flood event

On 12 July 1996 an isolated thunderstorm moved across the Buffalo and Spring Creek watersheds in the Front Range of the Rocky Mountains in Colorado, and produced more than 80-mm of precipitation during a one-hour period over both watersheds, causing a flash flood. Numerous factors were undoubtedly responsible for the mesoscale modulation of the large-scale, unstable, upslope flow such that the specific location and intensity of this storm were determined .

The objectives of this modeling study are to: 1) assess the skill of using the high-resolution coupled MM5/land-surface model to forecast flash-flood events in a complex terrain area with a 6-12 hour lead time; and 2) investigate the sensitivity of the simulation of this storm to the land-surface variability. In order to define the sensitivity of the rainfall location, timing and accumulation to the specification of the surface landscape properties for this heavy convective storm, a number of sensitivity studies were performed, wherein the surface conditions and the model physics were varied.

The model simulations are compared to the NCEP 4-km national precipitation analysis for validating the precipitation pattern at large-scales and to the S-Pol radar precipitation analysis for validating the flash-flooding prediction over the watershed. We discuss how the land-surface characteristics at local and regional scales can influence or enhance the predictability of convection in a complex terrain area.